Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.69	10.710%	$73.8325	$73.83	$73.85	$73.80
Purchase #2	$205.93	8.273%	$222.9666	$222.97	$222.95	$223.00
Purchase #3	$85.53	7.862%	$92.2544	$92.25	$92.25	$92.30
Purchase #4	$143.62	6.411%	$152.8275	$152.83	$152.85	$152.80
Purchase #5	$51.99	12.627%	$58.5548	$58.55	$58.55	$58.60
Purchase #6	$223.91	9.208%	$244.5276	$244.53	$244.55	$244.50
Purchase #7	$196.31	13.852%	$223.5029	$223.50	$223.50	$223.50
7 purchase totals =	$973.98		$1,068.4663	$1,068.46	$1,068.50	$1,068.50